Reuters Health

Saturday, February 8, 2003

Fri February 7, 2003 05:32 PM ET

NEW YORK (Reuters Health) - A gene that helps blood vessels form may play a key role in DiGeorge syndrome, one of the most common genetic causes of congenital heart defects.
DiGeorge syndrome affects about 1 in 4,000 infants, causing an array of problems including heart defects, facial abnormalities, immune dysfunction and blood disorders.

Researchers hope that by weeding out the genes behind the syndrome, they will someday be able to prevent or better treat the defects it causes.

DiGeorge has already been traced to a missing chunk of genes on chromosome 22. One of these genes, called Tbx1, is believed to be the primary culprit in the syndrome, but researchers have suspected other genes must certainly be involved.

For one, the specific defects vary widely among individuals with the disorder. And the group of genes that are deleted in DiGeorge syndrome oversee other, "downstream" genes, or those that rely on the missing genes for information.

The new study pinpoints one of these downstream genes as an important player in the syndrome's cardiovascular defects.

Researchers found that mice lacking one form of the vascular endothelial growth factor (VEGF) gene developed birth defects like those seen in DiGeorge syndrome.

VEGF is essential for proper blood vessel formation, and the new findings suggest that the VEGF gene interacts with Tbx1 to create cardiac defects, according to a report in the February issue of Nature Medicine.

Dr. Ingeborg Stalmans of Katholieke Universiteit in Leuven, Belgium, led the study.

Along with the mouse data, the researchers also discovered that DNA samples from DiGeorge patients showed an association between the syndrome and the VEGF "promoter"--a piece of DNA that governs how VEGF is expressed.

One of the next steps, according to the researchers, will be to try to find out why VEGF defects occur.